Sintered intermetallic bodies composed of aluminum and niobium or tantalum



United States Patent 3,231 344 SINTERED INTERMETALIZIC BQDKES CGMPOSED0F ALUMENUM AND NIOBTUM 0R TANTALUM Wallace W. Beaver, Shaker Heights,Robert M. Paine, Lakewood, and Albert James Stonehouse, Lyndhurst, Ohio,assignors to The Brush Beryilium Company, Cleveland, Ohio, acorporationofOhio No Drawing. Original application'ian. 22, 1963, SenNo.

253,064, now Patent No. 3,172,196, dated Mar. 9, 1965. Divided and thisapplication Dec. 14, 1964, Ser. No. 424,161

3 Claims. (Cl. 29-192) This is a division of application Serial No.253,064, filed January 22, 1963, now Patent No. 3,172,196, which is acontinuation of application Serial No. 27,523, filed May 9, 1950, nowabandoned.

This invention relates to binary intermetallic compound-compositions, tobodies composed thereof, and to "methods of making 'thecompound-compositions and bodies thereof.

The invention relates more specifically to binary intermetalliccompound-composition bodies which are of fine grain, havingsubstantially the theoretical density of the intermetalliccompound-composition 'of which they are composed, and which, attemperatures ranging from as high as 2000 F. to 2900 F., have extremelyhigh resistance to oxidation and extremely great strength.

Important features reside in the steps'of the preferred method by whichthe starting binary intermetallic compound-compositions in the powderedform are produced, and of the preferred method by which the powders areformed into the bodies having the physical properties above described.

Another feature is to form the bodies of the basic binary intermetalliccompound-compositions in which the metals are of such non-stoichiometricproportions as to increase the mechanical strength at the elevatedtemperatures over that which the bodies would have if the proportions ofthe two metals were stoichiometric.

I the present invention consist essentially of two metals,

one selected from a first group consisting of beryllium and aluminum,and another metal M selected from a second group consisting of niobium,zirconium, tantalum and molybdenum.

By the term consisting essentially of, it is meant to exclude any othermetal or materials subversive of the charactetistics of thesubstantially pure binary intermetallic compound-compositions.

The beryllium from the first group can be combined with any one of themetals from the second group. The

aluminum of the first group can be combined with any one of the metalsof the second group, but the outstanding advantages of the binaryintermetallic compoundcompositions containing aluminum are obtainableonly i when the aluminum is combined with either niobium or tantalum.

The ratio, by weight, of the metal of the first group to that of thesecond group can be any ratio desired in is obtainable.

3,231,344 Patented Jan. 25, 1966 a broad range wherein metal fromneither group is less than 20% of the combined weight of the two metals,the balance consisting essentially of a metal from the second group, andthe beryllium from the first group does not exceed substantially itsstoichiometric proportion corresponding to Mi3e and MBe and the aluminumfrom the first group does not exceed substantially its stoichiometricproportion corresponding to MAI wherein M is a metal selected from thegroup'consisting of niobium, zirconium, tantalum and molybdenum. Some ofthe metals, when used within more limited ratios within these broaderranges, have additional and particularly'outstanding qualities.

The metals of both groups preferably are substantially pure. For themost outstanding results, the binary intermetallic compoundacompositionshereof preferably have total impurities not exceeding about 1%, byweight, of their total weight.

The methods of producing the basic intermetallic compound-compositionsare as follows:

In one method, the selected metals, one from each roup, in the form ofpowder of particle size of about 50 mesh or finer, are intimatelyintermixed and reacted to completion. They may be reacted by melting inwhich case the resultant product is extremely hard and difficult topulverize'to form a powder for forming the final bodies.

The preferred methods are to effect the reactionof the metals in a solidstate, at sintering temperatures and below the temperature at whichappreciable melting or fusion would occur, to produce a friable compactof the binary intermetallic compound-compositions, which compact isreadily pulverizable to a particle size of about 200 mesh or finer. Inthe latter method, the two intimately intermixed metallic powders arefirst subjected to high mechanical pressure at room temperature to forma compact.

The compact is then charged into a graphite crucible, having amolybdenum liner, wherein the compact rests in the crucible on aberyllium oxide plate. 'The crucible mouth is covered with a berylliumoxide plate. The crucible is then subjected to vacuum in a furnace andthe pressure in the furnace is thereby lowered, preferably to less thanone micron of mercury.

Heat is then applied, starting at room temperature, preferably by meansof an adjustable electric resistance heating element so that accuratecontrol of the heating The heat is applied so as gradually to bring thecompact up to a temperature of about 450 C. During this initial heatingperiod, moisture and occluded and evolved gases are driven out of thecompact and drawn off by the vacuum pump from the crucible and compact.As they are evolved and freed, the furnace pressure tends to rise, butis maintained generally at less than ten microns, and preferably at lessthan one micron of mercury, by the continuance of the evacuation.

As one example of a compact, about cubic centimeters, by volume, of themixture of the two metallic powders are subjected preferably to about 30tons per square inch of mechanical pressure, at room temperature. Thisproduces a cold compact of about 65% of theoretical density.

As an alternate method, the compacting step may be omitted and theselected mixture of powdered metal may be reacted in loose form, theother steps, conditions, and proportions, remaining unchanged.

Compacting has the advantage of convenience in handling the metals andcharging the crucible. In addition, there is less danger ofcontamination of the charge by reaction with the container due tominimum surface contact in the case of the compact.

increased at the rate of about 100 C. per hour until it reaches a highertemperature of from about 1000 C. to 1400 C. This higher temperature,together with the vacuum, is continued for about one hour.

Next the heat is turned olf, and with the vacuum continued, the compactis allowed to cool to less than 100 C., after which it is removed fromthe furnace.

The exact period of time of heating may be varied considerably, thecontrolling limitation, however, being that if the heating is too rapid,the metallic powders melt or fuse to an extent which renders theresultant mass solid and unfriable.

When the gradual heating step is employed, the resultant compact is veryporous and friable and can be pulverized readily to a particle size of200 mesh or finer to provide the initial powder'for practicing theprocess of forming the bodies, as hereinafter described.

By starting with the recited' initial heating time of 16 hours, andgradually reducing it for each run, the optimum time for processing eachmixture can be established without loss of valuable metal.

In the foregoing sintering methods, an inert atmosphere 7 may besubstituted for the vacuum throughout the practice EXAMPLE1.BERYLLIUM-NIOBIUM Finely powdered beryllium, in an amount of 3.50kilograms, was intimately.mixed with 3.017 kilograms of the finelypowdered niobium, both materials being of a particle size of 50 mesh orfiner. The intimate intermixture was then compacted at room temperatureat a pressure of about 30 tons per square inch. The cold pressed compactwas placed in the graphite crucible in a furnace chamber which was thenevacuated while at room temperature to a pressure of less than onemicron of mercury. As soon as this degree of evacuation was reached,heat was applied and the compact heated gradually to 450 C., whilecontinuing the evacuation. The heating and evacuation were continueduntil the compact was substantially free from moisture and occludedgases and vapors. Thereupon the rate of heating was increased by about100 C. per hour until a maximum temperature of about 1270 C. wasreached, the vacuum meanwhile being continued. This maximum temperatureand concurrent evacuation were continued for about one hour. Thereuponthe heating was then discontinued, but with the vacuum continuing, thefurnace was cooled to room temperature. The product of this reaction wasa friable and porous compact. It was removed from the furnace and waseasily pulverized to powder having a particle size of 200 mesh or finer.The beryllium content determined by chemical analysis was 53.6% byweight, of the intermetallic compound-composition, the balanceconsisting essentially of niobium.

EXAMPLE 2.-BERYLLIUM-NIOBIUM The procedure of Example 1 was followedusing 535.4 grams of beryllium and 648.6 grams of niobium. The berylliumcontent, found by chemical analysis, was 45.2% by Weight of theintermetallic compound-composition, the balance consisting essentiallyof niobium.

4 EXAMPLE 3.BERYLLIUM-ZIRCONIUM The procedure of Example 1 was followedusing 3.461 kilograms of beryllium and 2.644 kilograms of zirconium. Bychemical analysis, the beryllium content was 56% by Weight of theintermetallic compound-composition, the balance consisting essentiallyof zirconium.

EXAMPLE 4.BERYLLIUM-ZIRCONIUM The procedure of Example 1 was followedusing 524.3 grams of beryllium and 622.7 grams zirconium. The berylliumcontent determined by chemical analysis was 45.7% by weight of theintermetallic compound-composition, the balance consisting essentiallyof zirconium.

EXAMPLE 5.BERYLLIUM-TANTALUM The procedure of Example 1 was followedusing 1.908 kilograms of beryllium and 3.192 kilograms of tantalum. Theberyllium content, determined by chemical analysis, was 37.2% 'by weightof the intermetallic compoundco-mposition, the balance consistingessentially of tantalum.

EXAMPLE 6.BERYLLIUM-TANTALUM The procedure of Example 1 was followedusing 540.2 grams of beryllium and 1247 grams of tantalum. The berylliumcontent, determined by chemical analysis, was 29.8% by Weight of theintermetallic compound-composition, the balance consisting essentiallyof tantalum.

EXAMPLE 7.BERYLLIUM-MOLYBDENUM The procedure of Example 1 was followedusing 2.676 kilograms of beryllium and 2.354 kilograms of molybdenum. Bychemical analysis, the beryllium content was 53% by weight of theintermetallic compound-composition, the balance consisting essentiallyof molybdenum.

EXAMPLE 8.ALUMINUM-NIOBIUM The procedure of'Example 1 was followed using282 grams of aluminum and 324 grams of niobium. The aluminum content,determined by chemical analysis, was 46.5% by weight of theintermetallic compound-composition, the balance consisting essentiallyof niobium.

EXAMPLE 9.-ALUMINUM-TANTALUM The procedure of Example 1 was followedusing 258 grams of aluminum and 577 grams of tantalum. By chemicalanalysis, the aluminum content was 30.9% by weight of the intermetalliccompound-composition, the balance consisting essentially of tantalum.

Having prepared the basic pulverized intermetallic compound-compositionpowder, the next step is to form any selected one of them into bodieshaving a fine grain, a density of substantially the calculatedtheoretical density, and high oxidation resistance and high strength attemperatures of from 2000-2900 F. To this end, the pulverizedintermetallic compound-composition powder, preferably of a particle sizeof 200 mesh or finer, is charged into a graphite die havingsubstantially the internal configuration desired for the exterior of thebody to be produced.

The charge and die are subjected, ina furnace at room temperature, toconcurrent evacuation and application of mechanical pressure of about1000 pounds per square inch. The evacuation and mechanical pressure arecontinued until the furnace chamber, with the charged die: therein, isevacuated to a furnace pressure not to exceedv 1000 microns of mercury,and preferably as low as 40'- microns of mercury. Beginning when thefurnace pressure has reached relative stability, indicating thatsubstantially all the gases and vapors have been removed, and With themechanical pressure and the vacuum continued, heat is I applied.

The temperature is increased and the mechanical pressure is concurrentlyincreased to a maximum of about 2000 pounds per square inch asthetemperature increases until substantially complete compaction andmaximum density are obtained, usually at about 1400 C. to about 1650 C.When this latter temperature and pressure are reached, the applicationof mechanical pressure is discontinued, but the vacuum and elevatedtemperature are continued thereafter until the stresses developed in thebody by the preceding steps are relieved. This latter step, which, ingeneral is an annealing step, generally requires about one-half hour forsmall compacts.

After the body is annealed, heating is discontinued and the furnace,die, and body are cooled gradually, under vacuum, to room temperature,after which the body is ready for removal and use.

As mentioned, the beryllium and aluminum may be used in amounts as lowas 20%, by weight of the body, up to but not to exceed stoichiometricproportions of, in the case of beryllium, MBe and. MBe and in the caseof aluminum, MAl wherein M is a metal selected from the group consistingof niobium, zirconium, tantalum and molybdenurmin any instance. Ifeither beryllium or aluminum is used in amounts less than stoichiometricproportions, it cannot with certainty besaid that the resultant materialis a true compound. Instead, it partakes somewhat of the nature both ofa true compound and a mixture of compounds.

A large number of intermetallic compound-compositions, some of which areof various phases, can be produced by selecting predetermined ratios ofthe selected starting powders.

The strength and oxidation resistance properties of the variousintermetallic compound-compositions, at the elevated temperatures, varyfor different proportions of the selected metals.

Generally, when a greater proportion of beryllium or aluminum than astoichiometric proportion of the more beryllium-rich, MBe and MBe andaluminum-rich, MAl respectively, compound-compositions of our. inventionis used as the upper limit of the range, in producing the binary.intermetallic compound-composition powders, the compound-compositionloses its high strength and oxidation resistance properties at theelevated temperatures. The loss of these desirable properties isbelieved to be attributable to the presence of free or unreactedberyllium or aluminum, either of which melts at a lower temperature than2350 F. In the case of very small amounts of the free metal, porosityand cracking result, and in the case of larger amounts, the meltingprevents the formation of a solid and dense body, at the hot-pressingtemperatures employed in our method. These upper substantiallystoichiometric limits of beryllium-or aluminum of the aboveberyllium-rich and aluminum-rich compound-compositions of our inventionare the upper critical limits, and preferably should not be exceeded atall, and certainly by not more than a small fraction of a percent.Surprisingly, the inclusion of these metals in less than stoichiometricproportions produces, in some instances, the greatest mechanicalstrength at elevated temperatures.

On the other hand, the lower limits of the specified ranges of berylliumand aluminum are not as critical, since the intermetalliccompound-compositions containing ten to fifteen percent, by weight, ofberyllium or aluminum are nevertheless of high melting point. Therecited ranges, however, cover those intermetallic compound-compositionswhich exhibit the most favorable grain size, density, oxidationresistance, and high strength, at elevated temperatures from 2000-2900"F.

It should be realized that the metal powders employed in the preparationof the intermetallic compound-compositions, as in the case of mostmetals, contained minor impurities. However, the beryllium powder usedwas 99.0% or more pure, and contained mainly beryllium oxide and veryminor amounts of heavy metals and aluminum as impurities. Such highpurity is preferred, but impurities up to about 3% may be tolerated insome instances. The

6 niobium, tantalum, molybdenum, and zirconium powders used were atleast about 99.5%pure.

Analysis-of the examples hereinafter given discloses.

Percent by weight of binary intermetallic compoundcomposition Impurity CCr, Ni, Mg, Mn (total) The strength and oxidation resistance propertiesof bodies of a large number of the binary intermetalliccompound-compositions of the present invention were evaluated bywellknown modulus-of-rupture and gain-in- Weight oxidation testingprocedures. These and other results are presented in Tables I and IIincluded hereinbelow. Said tables are referenced in some instances tothe specific examples included in this specification. The gain-in-weightdata were obtained by exposing weighed specimen bodies of eachintermetallic compound-composition to a cubic centimeter per minute flowof either dry or moist air for 100 hours at the respective temperaturesindicated in Table II hereof. The specimens were then re-weighed todetermine the increase in weight which is representative of theoxidation resistance for each composition.

The penetration data, also indic-ative of the oxidation resistance ofthese compositions, were calculated from the gain-in-weight data, on theassumption that the gains occurred by oxidation and that allcompositions oxidized stoichiometrically. The compoundcompositions whichshowed penetration of less than 2 mils in 100 hour exposure areconsidered to havegood oxidation resistance in the indicated temperatureranges.

Examples of the method of forming the bodies, and physical properties ofthe formed bodies follow. Some of the relevant data are tabulated andreferenced in Tables I and II by reference .to their example numbers.

Examples of the formation of bodies by the foregoing method are asfollows:

EXAMPLE. l0 (SPECIMEN A OF TABLES) An intermetallic compound-compositionpowder, in an amount :of 176.4 grams, consisting of 53.6%, by weight, ofberyllium and the balance consisting essentially of niobium, and havinga particle size of 200 mesh or finer, was placed in a furnace in agraphite die and mechanical pressure at about 1000 pounds per squareinch was then applied to the powder composition and then initiallyevacuated while at room temperature. Beginning when the gases and vaporswere substantially evacuated, heat was applied while maintainingmechanical pressure and vacuum. The temperature was increased graduallyand the mechanical pressure was concurrently increased, the vacuumconcurrently being continued, until a temperature of about 1550 C. and apressure of about 2000 psi were reached. The mechanical pressure wasthen discontinued, the vacuum and temperature being continued for aboutanother 20 minutes. Thereupon, the heating was discontinned, and thefurnace was allowed to cool, undervacuum, to room temperature. The body,upon removal from the furnace, weighed 167.6 grams and had a density of2.88 g./cc., which is 98% of the calculated theoretical density. Thegrain size was 11 microns, and the beryllium content, determined bychemical analysis, was-53.6%, by weight, of the body, the balanceconsisting essentially of niobium.

The furnace pressure reached during the initial substantial evacuationof the gases and vapors varies with different charges, the controllingfeature being the substantial removal of gases and vapors. In thisspecific example, the furnace pressure Was 170 microns of mercury. Thesubsequent evacuation was sufficient to rapidly remove the gases andvapors evolved during the heating and pressing, and in this example, thepressure ranged from 500 to 1000 microns of mercury.

EXAMPLE 11 (SPECIMEN B OF TABLES) An intermetallic compound-compositionpowder, in an amount of 254 grams, consisting of 51.6%, by weight, ofberyllium, with the balance consisting essentially of piobium, andhaving a particle size of 200 mesh or finer, was placed in a graphitedie in a furnace. Following the procedure of Example 10, the temperatureand mechanical pressure were increased to a maximum of about 15 20 C.and 2000 p.s.i. concurrently during the maintenance of the vacuum. Themechanical pressure was then discontinued, and the concurrent maximumtemperature and vacuum maintained for about a half hour, after whichtime the heating was discontinued, and the furnace cooled under vacuumto room temperature. The body, upon removal from the furnace, weighed217.5 grams, and had a density of 2.99 g./cc., which is 99.7% of thecalculated theoretical density. *Upon chemical analysis, its berylliumcontent was found to be 51.6%, by weight, of the body, with the balanceconsisting essentially of niobium, and its grain size was 15 microns.

The furnace pressure during the initial evacuation was 500 microns ofmercury, and during the subsequent evacuation ranged from 300 to 500microns of mercury.

EXAMPLE 12 (SPECIMEN E OF TABLES) Following the procedure of Example 10,309 grams of powdered intermetallic compound-composition consisting of46.4% by weight of beryllium, and the balance consisting essentially ofniobium, and having a particle size of 200 mesh or finer, were placed inthe die. During the concurrent maintenance of temperature, mechanicalpressure, and vacuum, the gradual increase was to a maximum temperatureof about 1520 C. and to a mechanical pressure of about 2000 p.s.i. Thepressure was then discontinued and the concurrent maximum temperatureand evacuation were continued for about a half hour, after which theheating was discontinued and the furnace cooled under vacuum to roomtemperature. The body, upon removal from the furnace, weighed 297 gramsand had a density of 3.08 g./cc., which is 97.5% of the calculatedtheoretical density. The grain size was 15 microns and chemical analysisshowed the body to contain beryllium in an amount, by weight, of 46.4%of the body, with the balance consisting essentially of niobium.

The pressure during the initial substantial evacuation was 200 micronsof mercury, and during the subsequent evacuation ranged from 180 to 250microns of mercury.

EXAMPLE 13 (SPECIMEN F OF TABLES) Following the procedure of Example 10,264 grams of an intermetallic compound-composition consisting of 45.2%,by weight, of beryllium and the balance consisting essentially ofniobium, in powder form, and having a particle size of 200 mesh orfiner, were introduced into a die. The increase in temperature andpressure were to a maximum temperature of about 1550 C. and a maximummechanical pressure of about 2000 p.s.i., the pressure, vacuum, andtemperature application being maintained concurrently. When the maximumtemperature Was reached, the pressure was discontinued, and concurrentevacuation and the maximum temperature were maintained for about a halfhour. The heating was then discontinued, and the furnace cooled undervacuum to room temperature. Upon removal from the furnace, the bodyweighed 235 grams, and had a density of 99.4% of the calculatedtheoretical density, with a grain size of 8 9 microns. Chemical analysisshowed it to contain beryllium in an amount, by weight, of 45.2% of thebody, with the balance consisting essentially of niobium.

The pressure during the initial substantial evacuation Was 40 microns ofmercury, and during the subsequent evacuation, ranged from 100 to 250microns of mercury.

EXAMPLE l4 (SPECIMEN G OF TABLES) V 200 mesh of finer, was introducedinto the die within a furnace I Following the roceduie'or Example 10,'

the furnace was evacuated concurrently with the application of about1000 p.s.i. of mechanical pressure, The vacuum was maintained and heatwas applied, accompanied by a concurrent increase of mechanicalpressure. During the concurrent evacuation and application of mechanicalpressure and heat, a maximum temperature of about 1550 C. and a maximumpressure of about 2000 p.s.i. were attained. At this time, the pressurewas discontinued, and the evacuation and temperature were maintainedconcurrently for about a half hour, after which time the furnace and diewere cooled under vacuum to room temperature. The body, upon removalfrom the furnace, weighed 154.9 grams, and had a density of 2.77 g./cc.,which is 99.3% of the calculated theoretical density. The grain size 25microns. The body was found by chemical analysis to contain beryllium inan amount equal to 56% of the body, with the balance substantially onlyzirconium.

The pressure during the initial substantial evacuation was 180 micronsof mercury, and during the subsequent evacuation, was about 1000 micronsof mercury.

EXAMPLE l5 (SPECIMEN I OF TABLES) In accordance with the procedure ofExample 10, 513 grams of an intermetallic compound-composition in powderform, consisting of 51.5% by weight of beryllium and the balanceconsisting essentially of zirconium, and having a particle size of 200mesh or finer, were introduced into the die in a furnace. During theconcurrent application of heat, mechanical pressure and evacuation, theincrease of temperature was up to a maximum temperature of about 1550 C.The increase in mechanical pressure was up to a maximum of about 2000p.s.i. The maximum pressure was then discontinued, and the maximumtemperature, with evacuation, maintained for about 40 minutes. Theheating was then discontinued, and the furnace allowed to cool to roomtemperature, under vacuum. The body, upon removal, weighed 488.6 grams,and had a density of 2.84 g./cc., corresponding to 98.6% of thecalculated theoretical density. The grain size was 24 microns. Chemicalanalysis disclosed 51.5% of beryllium by weight, of the body, and thebalance consisting essentially of zirconium.

The pressure during the initial substantial evacuation was microns ofmercury, and during the subsequent evacuation ranged from 75 to 150microns of mercury.

EXAMPLE 16 (SPECIMEN M OF TABLES) Following the procedure of Example 10,240 grams of an intermetallic compound-composition powder, consisting of45.7% by weight of beryllium, the balance consisting essentially ofzirconium, and having a particle size of 200 mesh or finer, wereintroduced into the die. During the evacuation with a concurrentincrease in mechanical pressure and in temperature, a maximumtemperature of about 1550 C. and a maximum mechanical pressure of about2000 p.s.i. were attained. The mechanical pressure was thendiscontinued, and the concurrent evacuation and maximum temperaturemaintained for about a half hour, after which time the heating wasdiscontinued and the furnace vacuum cooled to room temperature. Thebody, upon removal, weighed 225 grams,

and had a density of 3.06 g./cc., corresponding to 100% of thecalculated theoretical density. The grain size was 30 microns, andchemical analysis showed the body to contain beryllium in an amount45.7% by weight, of the.

body, the balance consisting essentially of zirconium.

The pressure during the initial substantial evacuation was 40 microns ofmercury, and during the subsequent evacuation ranged from 200 to 500microns of mercury.

EXAMPLE 17 (SPECIMEN N OF TABLES) In accordance with the procedure ofExample 10, an intermetallic compound-composition in powder form, in anamount of 345 grams, and consisting of 37.2% by weight of beryllium andthe balance consisting essentially of tantalum, and having a particlesize of. 200 mesh or finer, was introduced into the die, and the furnacewas then evacuated while applying about 1000 p.s.i. of mechanicalpressure. When the furnace was substantially evacuated, heat was appliedand increased, accompanied by a concurrent increase in the mechanicalpressure to about 1550 C. and about 2000 p.s.i. Thereupon, the pressurewas discontinued, and the maximum temperature and concurrent evacuationwas maintained for about a half hour, after which time the heating wasdiscontinued, and the furnace vacuum cooled to room temperature. Thebody, when removed, weighed 328 grams and had a density of 4.11 g./cc.,corresponding to 96.9% of the calculated theoretical density. The grainsize was 12 microns, and chemical analysis showed 37.2% by weight ofberyllium with the balance consisting essentially of tantalum.

The pressure during the initial substantial evacuation was 800 micronsof mercury, and during the subsequent evacuation was about 800 micronsof mercury.

EXAMPLE 18 (SPECIMEN Q OF TABLES) In accordance with the procedure ofExample 10, 900

grams of an intermetallic compound-composition consisting of 29.8% byweight of beryllium and the balance consisting essentially of tantalum,and having a particle size of 200 mesh or finer is disposed in thegraphite die in a furnace. During the concurrent evacuation, andapplication of increasing heat and pressure, the maximum temperatureattained was about 1550 C. and maximum mechanical pressure of about 2000psi. When these maximums were reached, the mechanical pressure wasdiscontinued and the evacuation and maximum temperature continued forabout a half hour. The heating was then discontinued, the vacuummaintained, and the furnace and die cooled to room temperature. Thebody, when removed, weighed 855.5 grams and had a density of 4.88g./cc., corresponding to 96% of the calculated theoretical density. Thegrain size was 18 microns.

Chemical analysis showed 29.8% of beryllium, by weight of the body, thebalance consisting essentially of tantalum:

The pressure during the initial substantial evacuation was 200 micronsof mercury, and during the subsequent evacuation ranged from 175 to 250microns of mercury..

EXAMPLE 19 (SPECIMEN R OF TABLES) In accordance with the procedure ofExample 10, 250 grams of an intermetallic compound-compositionconsisting of 53% by weight of beryllium and the balance consistingessentially of molybdenum, and having a particle size of 200 mesh orfiner, were introduced in the die in a furnace. During the concurrentevacuation and the increase in application of mechanical pressure andheat, a maximum temperature of about 1550 C. and a maximum pressure ofabout 2000 p.s.i. were reached. As soon as this maximum temperature wasreached, the pressure was discontinued, and the concurrent maximumtemperature and the evacuation were continued for about a half hour. Theheating was then discontinued, the vacuum continued until the furnace iscooled to room temperature. The body weighed 236 grams, and had adensity of 3:02 g./cc. corresponding to 97.7% of the calculatedtheoretical density. The grain size was 16 microns and chemical analysisshowed 53% beryllium by weight of the body, the balance consistingessentially of molybdenurn.

The press during the initial substantial evacuation was 45 microns ofmercury, and during the subsequent eva uation ranged from 200 to 500microns of mercury.

EXAMPLE 2O (SPECIMEN S OF TABLES) An intermetallic compound-composition,in an amount of 205.65 grams, and consisting of 46.5% by weight ofaluminum and the balance consisting essentially of niobium, and having aparticle size of 200 mesh or finer, was introduced in the graphite die.In accordance with the procedure of Example 10, the furnace was thenevacuated at room temperature during a concurrent application of about1000 p.s.i. mechanical pressure. When the furnace was substantiallyevacuated, heat was applied and the pressure was concurrently graduallyincreased, the evacuation being continued. The concurrent evacuation,application of heat, and increase in mechanical pressure continued untila maximum temperature of about 1465 C. and a maximum pressure of about2000 p.s.i. were reached. The pressure was then discontinued, and theconcurrent maximum temperature and evacuation maintained for about ahalf hour, after which the heating was discontinued, the vacuumcontinued and the furnace cooled to room temperature. The body was thenre moved from the furnace. It weighed 197.5 grams, and had a density of4.36 g./cc., which corresponds to 95.4% of the calculated theoreticaldensity. The grain size was 25 microns and chemical analysis showed46.5% aluminum by weight of the body, with the balance consistingessentially of niobium.

EXAMPLE 21 (SPECIMEN T OF TABLES) Following the procedure of Example 10,346 grams of an intermetallic compound-composition consisting of 30.9%by weight of aluminum and the balance consisting essentially oftantalum, and having a particle size of 200 mesh or finer, wereintroduced into a graphite die located in a furnace. During theconcurrent evacuation and increase of heat and mechanical pressure, amaximum temperature of about 1465 C. and a maximum pressure of about2000 p.s.i. were reached. As soon as the maximum temperature andpressure were reached, the mechanical pressure was discontinued, and themaximum temperature and evacuation maintained for about a half hour.With the evacuation continuing, the furnace was cooled to roomtemperature. The body was then removed, and weighed 288.8 grams, and hada density of 6.60 g./cc., which corresponds to 95.4% of the calculatedtheoretical density. Chemical analysis showed 30.9% aluminum, by weightof the body, with the balance consisting essentially of ltantalum.

TABLE I TRANSVERSE-RUPTURE STRENGTH DATA FOR INTERMETALLICCOMPOUND-COMPOSITIONS Having thus described our invention, we claim:

1. A sintered body, having predetermined size and shape which have beenimparted to it by the cavity walls of a die, and having high strengthand oxidation resistance at temperatures ranging from about 2000 F. toabout 2700 F., and consisting essentially of aluminum and a metal Mwhich is selected from the group consisting of niobium and tantalum,said aluminum being present up to about, but not to exceed substantiallyits stoichiometrio proportion corresponding to; MAL- by Weight, of thebody, and the balance being the metal M, and said body having fine grainand substantially theoretical density.

2. A sintered body, having predetermined size and shape which have beenimparted to it by the cavity walls of a die, and having high strengthand oxidation resistance at temperatures ranging from about 2000 F. toabout 2900 F., and consisting essentially of aluminum of no more thansubstantially 46.5%, by weight, of the body, the balance consistingessentially of niobium, and

said body having fine grain and substantially theoretical density.

3. A sintered body, having predetermined size and shape which have beenimparted to it by the cavity walls of a die, and having high strengthand oxidation resistance at temperatures ranging from about 2000 F. toabout 2900 F., and consisting essentially of aluminum of not more thansubstantially 30.9%, by weight, of the body, the balance consistingessentially of tantalum, and said body having fine grain andsubstantially theoretical density.

References Cited by the Examiner UNITED STATES PATENTS 2,885,286 5/1959Weber 75-138 2,905,549 9/1959 Taylor et al. 75138 2,966,736 1/1961Towner et al. 75138 DAVID L. RECK, Primary Examiner. HYLAND BIZOT,Examiner.

1. A SINTERED BODY, HAVING PREDETERMINED SIZE AND SHAPE WHICH HAVE BEENIMPARTED TO IT BY THE CAVITY WALLS OF A DIE, AND HAVING HIGH STRENGTHAND OXIDATION RESISTANCE AT TEMPERATURES RANGING FROM ABOUT 2000*F. TOABOUT 2700*F., AND CONSISTING ESSENTIALLY OF ALUMINUM AND A METAL MWHICH IS SELECTED FROM THE GROUP CONSISTING OF NIOBIUM AND TANTALUM,SAID ALUMINUM BEING PRESENT UP TO ABOUT, BUT NOT TO EXCEED SUBSTANTIALLYITS STOICHIOMETRIC PROPORTION CORRESPONDING TO MAL3, BY WEIGHT, OF THEBODY, AND THE BALANCE BEING THE METAL M, AND SAID BODY HAVING FINE GRAINAND SUBSTANTIALLY THEORETICAL DENSITY.